1. Field of the Invention
The present invention relates to trays used by laboratory technicians in making a dental model from casting material that is poured on the tray.
2. State of the Art
Dental trays have been used in the prior art wherein casting material is poured on the tray and a dental model is then formed in the casting material. A system in the prior art utilized a plurality of metal pins that extended upwardly from the upper surface of the tray, with the casting material being poured over the pins. The resulting dental model could then be cut so as to isolate one or more dies corresponding to teeth upon which a crown or other prosthetic device was to be formed. The die or dies could then be placed back on the tray, and the correspondence of the pins extending from the tray into the die or dies would result in proper positioning of the die or dies relative to the dental model.
A problem with the tray having metal pins is that the metal pins must be formed by precision machining and thus the trays are relatively very expensive. Dental labs are very reluctant to use the trays because of their exorbitant cost. It would be highly desirable to produce an inexpensive tray that did not use the expensive machined metal pins, such as a tray made of polymeric material in which the pins are formed integrally with the tray from the same polymeric material. Unfortunately, if one makes a tray of polymeric material having pins made of the same polymeric material, with the pins being spaced apart and shaped similar to the metal pins of the prior art trays, the tray with pins made of polymeric material is totally useless. The tray has shortcomings that prevent it from being a viable tool to be used in making a satisfactory dental model.
The metal pins of the prior art dental tray are sufficiently rigid to retain dies that have been cut from a dental model that has been cast in place on the dental tray. However, with pins made of polymeric material and having a similar size and shape as the metal pins of the trays of the prior art, the resulting pins made of polymeric material are too flexible and do not have sufficient rigidity. A dental model can be cast on such pins, but when the dental model is cut into dies, and the dies are replaced on their mutually respective pins, the individual dies are not stable, i.e., the pins flex and allow the dies to move to and away from adjacent dies or adjacent portions of the model. This is because the pins made of polymeric material are not sufficiently rigid, they flex and thus allow do not hold the dies firmly in their proper orientation. Cutting of the dies from the model results in a portion of the die equal to the thickness of the saw being removed from the die. When the die is replaced in the model there is a space equivalent to the thickness of the saw on each side of the die. When the pins are not sufficiently rigid to prevent the die from moving back and forth within that space formed by the saw cuts, then the die cannot be used in forming a precision prosthetic thereon, and the resulting dental model is not useful.